Polymer derived carbon ceramics are highly desirable for lightweight, high strength, extreme environment material architectures, but their mechanical performance as a function of structure and processing is not currently understood and cannot be predicted. In this study, the mechanical behavior for bulk-scale pyrolytic carbons (PyCs) made via polymer pyrolysis of phenolformaldehyde precursors are established as a function of heat treatment temperature and the resulting average nano-and meso-scale order and disorder via X-ray diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy. The PyCs exhibit crystallite evolution on both the atomic-and meso-scale for pyrolysis temperatures of 600 • C to 1000 • C, whereas only atomic-scale crystallite evolution is observed for pyrolysis temperatures of 1000 • C to 1400 • C. The measured Vickers hardness of the PyCs is observed to scale non-monotonically as a function of the pyrolysis temperature reaching a peak at ∼ 4 GPa for samples prepared at 1000 • C. New modeling results, based on the elastic constants of disordered graphite, indicate that this counter-intuitive Vickers hardness scaling, which is a decades-old open question, originates from the PyC inter-layer shear elastic constant and the crystallite aspect ratio evolution with processing temperature. PyCs studied here are shown to be the lightest super-hard materials, having Vickers hardness-to-density ratios that are comparable to super-hard carbides, oxides, nitrides, and phosphides.

Materials comprising carbon nanotube (CNT) aligned nanowire (NW) polymer nanocom-\ud posites (A-PNCs) are emerging as next-generation materials for use in aerospace structures.\ud Enhanced operating regimes, such as operating temperatures, motivate the study of CNT\ud aligned NW ceramic matrix nanocomposites (A-CMNCs). Here we report the synthesis of\ud CNT A-CMNCs through the pyrolysis of CNT A-PNC precursors, thereby creating carbon\ud matrix CNT A-CMNCs. Characterization reveals that the fabrication of high strength,\ud high temperature, lightweight next-generation aerospace materials is possible using this\ud method. Additional characterization and modeling are planned